Chemistry

"Neither is it impossible that of these minute Particles divers of the smallest and neighbouring ones were here and there associated into minute Masses or Clusters, and did by their Coalitions constitute great store of such little primary Concretions or Masses as were not easily dissipable into such Particles as compos'd them."

"It seems not absurd to conceive that at the first Production of mixt Bodies, the Universal Matter whereof they among other Parts of the Universe consisted, was actually divided into little Particles of several sizes and shapes variously mov'd."

"Who sees the future? Let us have free scope for all directions of research; away with dogmatism, either atomistic or anti-atomistic!"

"We have come a long way from the classical ideal of objective descriptions. In quantum mechanics the departure from this ideal has been even more radical. We can still use the objectifying language of classical physics to make statements about observable facts. For instance, we can say that a photographic plate has been blackened, or that cloud droplets have formed. But we can say nothing about the atoms themselves."

"In 1763 a Croatian Jesuit named Roger Joseph Boscovich (1711 - 1787) identified the ultimate implication of this mechanical atomic theory. One of the crucial aspects of Isaac Newton's laws of motion is their predictive capability. If we know how an object is moving at any instant - how fast, and in which direction - and if, furthermore, we know the forces acting on it, we can calculate its future trajectory exactly. This predictability made it possible for astronomers to use Newton's laws of motion and gravity to calculate, for example, when future solar eclipses would happen. Boscovich realized that if all the world is just atoms in motion and collision, then an all-seeing mind "could, from a continuous arc described in an interval of time, no matter how small, by all points of matter, derive the law [that is, a universal map] of forces itself … Now, if the law of forces were known, and the position, velocity and direction of all the points at any given instant, it would be possible for a mind of this type to foresee all the necessary subsequent motions and states, and to predict all the phenomena that necessarily followed from them.""

"In general, the rate of evaporation (m) of a substance in a high vacuum is related to the pressure (p) of the saturated vapor by the equation m=\sqrt{\frac{M}{2\pi RT}}p. Red phosphorus and some other substances probably form exceptions to this rule."

"Researchers hope to be able to get diffraction patterns from individual molecules, allowing them to watch biomolecules moving and interacting in a completely natural setting, surrounded by water, instead of trapped in the artificial environment of a crystal. That’s my future vision for crystallography. Get away from being a coroner imaging dead molecules, and instead get molecular movies."

"Crystallographers should take a lesson from particle physicists and create a body run by scientists for the governance of large international x-ray and neutron facilities. It should be guided by input from regular meetings of researchers from across the scientific community. This will ensure that the next generation of infrastructure will have the strongest possible scientific case, articulated clearly."

"Crystallography remains a cutting-edge field, and one that, if harnessed properly, could contribute as much in the next 100 years as it did in the previous 100. The development of the x-ray free-electron laser, for example, is a monumental technical achievement, and one that seems more suited to the world of 2114 than 1914, or even 2014."

"Thanks to the methods that [Crystallographers] have devised for investigating crystal structures, an entirely new world has been opened and has already in part been explored with marvelous exactitude. The significance of these methods, and of the results attained by their means, cannot as yet be gauged in its entirety, however imposing its dimensions already appear to be."

"It takes a very special breed of scientist to do this work...it is an area of science in which women dominate."

"Crystallographers have a raft of methods at their disposal. Von Laue scattered X-ray photons from atoms. Now experimenters can also bombard crystal lattices with electrons and neutrons, and exploit properties such as the polarization of photons and neutrons and their interactions with magnetic fields."

"Crystallography is increasingly focusing its resources on large multidisciplinary facilities, such as powerful X-ray and neutron sources."

"Aeroplanes fly safely because crystallography tests computer models of materials under stress. Drugs are more potent because crystallographers can see and modify how molecules interact with target sites in cells. An X-ray diffraction instrument on NASA’s Curiosity rover is now even studying the mineralogy of Mars."

"Since modern crystallography dawned with X-ray diffraction experiments on crystals by Max von Laue in 1912 and William and Lawrence Bragg (a father and son team) in 1913, and was recognized by Nobel prizes in physics for von Laue in 1914 and the Braggs in 1915, the discipline has informed almost every branch of the natural sciences."

"I miss the old days, when nearly every problem in X-ray crystallography was a puzzle that could be solved only by much thinking."

"...all the work of the crystallographers serves only to demonstrate that there is only variety everywhere they suppose uniformity...that innature there is nothing absolute, nothing perfectly regular."

"In my own field, x-ray crystallography, we used to work out the structure of minerals by various dodges which we never bothered to write down, we just used them. Then Linus Pauling came along to the laboratory, saw what we were doing and wrote out what we now call Pauling's Rules. We had all been using Pauling's Rules for about three or four years before Pauling told us what the rules were."

"Net molecular polarity is measured by a quantity called the dipole moment and can be thought of in the following way: assume that there is a center of mass of all positive charges (nuclei) in a molecule and a center of mass of all negative charges (electrons). If these two centers don’t coincide, then the molecule has a net polarity. The dipole moment, μ (Greek mu), is defined as the magnitude of the charge Q at either end of the molecular dipole times the distance r between the charges, μ = Q × r. Dipole moments are expressed in debyes(D), where 1 D = 3.336 ×10-30 coulomb meter (C · m) in SI units. For example, the unit charge on an electron is 1.60 ×10-19 C. Thus, if one positive charge and one negative charge are separated by 100 pm (a bit less than the length of a typical covalent bond), the dipole moment is 1.60 ×10-29 C · m, or 4.80 D.… In contrast with water, methanol, and ammonia, molecules such as carbon dioxide, methane, ethane, and benzene have zero dipole moments. Because of the symmetrical structures of these molecules, the individual bond polarities and lone-pair contributions exactly cancel."

"Deep in the sea all molecules repeat the patterns of one another till complex new ones are formed. They make others like themselves and a new dance starts.Growing in size and complexity living things masses of atoms DNA, protein dancing a pattern ever more intricate."

"Organic molecules are usually drawn using either condensed structures or skeletal structures. In condensed structures, carbon–carbon and carbon–hydrogen bonds aren’t shown. In skeletal structures, only the bonds and not the atoms are shown. A carbon atom is assumed to be at the ends and at the junctions of lines (bonds), and the correct number of hydrogens is mentally supplied."

"Valence electrons that are not used for bonding are called lone-pair electrons, or nonbonding electrons. … As a time-saving shorthand, nonbonding electrons are often omitted when drawing line-bond structures, but you still have to keep them in mind since they’re often crucial in chemical reactions."

"A simple way of indicating the covalent bonds in molecules is to use what are called Lewis structures, or electron-dot structures, in which the valence shell electrons of an atom are represented as dots. … Simpler still is the use of Kekulé structures, or line-bond structures, in which a two-electron covalent bond is indicated as a line drawn between atoms."

"MOLECULE, n. The ultimate, indivisible unit of matter. It is distinguished from the corpuscle, also the ultimate, indivisible unit of matter, by a closer resemblance to the atom, also the ultimate, indivisible unit of matter. Three great scientific theories of the structure of the universe are the molecular, the corpuscular and the atomic. A fourth affirms, with Haeckel, the condensation of precipitation of matter from ether -- whose existence is proved by the condensation of precipitation. The present trend of scientific thought is toward the theory of ions. The ion differs from the molecule, the corpuscle and the atom in that it is an ion. A fifth theory is held by idiots, but it is doubtful if they know any more about the matter than the others."

"A diatomic molecule is a molecule with one atom too many."

"Such a shared-electron bond, first proposed in 1916 by G. N. Lewis, is called a covalent bond. The neutral collection of atoms held together by covalent bonds is called a molecule."

"The carbohydrates are naturally organic compounds containing carbon,hydrogen and oxygen.Their ratio of hydrogen to oxygen in water is 2:1,the no.of simpler carbohydrate molecules obtained upon hydrolysis determines the class of a particular carbon hydrate."

"A substance showing resonance between two or more valence-bond structures does not contain molecules with the configurations and properties usually associated with these structures."

"Although each individual resonance form seems to imply that benzene has alternating single and double bonds, neither form is correct by itself. The true benzene structure is a hybrid of the two individual forms, and all six carbon–carbon bonds are equivalent. This symmetrical distribution of electrons around the molecule is evident in an electrostatic potential map."

"Some molecules cannot be described accurately by one Lewis structure but exist as hybrids of several resonance forms. To find the most important resonance contributor, consider the octet rule, make sure that there is a minimum of charge separation, and place on the relatively more electronegative atoms as much negative and as little positive charge as possible."

"Does the carbonate ion have one uncharged oxygen atom bound to carbon through a double bond and two other oxygen atoms bound through a single bond each, both bearing a negative charge, as suggested by the Lewis structures? Or, to put it differently, are A, B, and C equilibrating isomers? The answer is no... It is said to be delocalized, in accord with the tendency of electrons to “spread out in space”. In other words, none of the individual Lewis representations of this molecule is correct on its own. Rather, the true structure is a composite of A, B, and C. The resulting picture is called a resonance hybrid."

"When first dealing with resonance forms, it’s useful to have a set of guidelines that describe how to draw and interpret them. The following rules should be helpful: … Individual resonance forms are imaginary, not real. … Resonance forms differ only in the placement of their π or nonbonding electrons. … Different resonance forms of a substance don’t have to be equivalent. … Resonance forms obey normal rules of valency. … The resonance hybrid is more stable than any individual resonance form."

"The fine-tuning of the universe, about which cosmologists make such a to-do, is both complex and specified and readily yields design. So too, Michael Behe's irreducibly complex biochemical systems readily yield design. The complexity-specification criterion demonstrates that design pervades cosmology and biology. Moreover, it is a transcendent design, not reducible to the physical world. Indeed, no intelligent agent who is strictly physical could have presided over the origin of the universe or the origin of life."

"Q: Strange, isn't it, Jean-Luc? Everything you know... your entire civilization... it all begins right here in this little pond of goo. It's appropriate somehow, isn't it? Too bad you didn't bring a microscope -- this is quite fascinating. Here they go... the amino acids are moving closer... closer...closer...Ohhhh! Nothing happened! You see what you've done?"

"You know, my brothers, the nature of our business. The child you see before you, thanks to a talisman stolen from the powers of Earth, is able to take possession of the Blue Bird and thus to snatch from us the secret which we have kept since the origin of life... Now we know enough of Man to entertain no doubt as to the fate which he reserves for us once he is in possession of this secret. That is why it seems to me that any hesitation would be both foolish and criminal... It is a serious moment; the child must be done away with before it is too late..."

"Believing the first cell originated by chance is like believing a tornado ripping through a junkyard full of airplane parts could produce a Boeing 747."

"Life could spread from planet to planet or from stellar system to stellar system, carried on meteors."

"It is as though a puzzle could be put together simply by shaking its pieces."

"It is mere rubbish thinking, at present, of origin of life; one might as well think of origin of matter. —"

"An example of such emergent phenomena is the origin of life from non-living chemical compounds in the oldest, lifeless oceans of the earth. Here, aided by the radiation energy received from the sun, countless chemical materials were synthesized and accumulated in such a way that they constituted, as it were, a primeval “soup.” In this primeval soup, by infinite variations of lifeless growth and decay of substances during some billions of years, the way of life was ultimately reached, with its metabolism characterized by selective assimilation and dissimulation as end stations of a sluiced and canalized flow of free chemical energy."

"The world has arisen in some way or another. How it originated is the great question, and Darwin's theory, like all other attempts to explain the origin of life, is thus far merely conjectural. I believe he has not even made the best conjecture possible in the present state of our knowledge."

"The synthesis of pure, calming food is breathing pure air, listening to good sounds, looking at good sights, and touching pure objects."

"There is synthesis when, in combining therein judgments that are made known to us from simpler relations, one deduces judgments from them relative to more complicated relations. There is analysis when from a complicated truth one deduces more simple truths."

"The overall yield in a multistep step synthesis is the product of the yields for each separate step. In a linear synthetic scheme, the hypothetical TM is assembled in a stepwise manner. … Since the overall yield of the TM decreases as the number of individual steps increases, a convergent synthesis should be considered in which two or more fragments of the TM are prepared separately and then joined at the latest-possible stage of the synthesis. It should be noted, however, that the simple overall yield calculation is some- what misleading since it is computed on one starting material, whereas several are used and the number of reactions is the same! Nevertheless, the increased efficiency of a convergent synthesis compared to the linear approach is derived from the fact that the preparation of a certain amount of a product can be carried out on a smaller scale."

"Get the habit of analysis- analysis will in time enable synthesis to become your habit of mind."

"Synthetic method is that which begins with the parts, and leads onward to the knowledge of the whole : it begins with the most simple principles and general truths, and proceeds by degrees to that which is drawn from them, or compounded of them ; and therefore it is called the method of composition."

"Analysis and synthesis ordinarily clarify matters for us about as much as taking a Swiss watch apart and dumping its wheels, springs, hands, threads, pivots, screws and gears into a layman's hands for reassembling, clarifies a watch to a layman."

"We are approaching a new age of synthesis. Knowledge cannot be merely a degree or a skill... it demands a broader vision, capabilities in critical thinking and logical deduction without which we cannot have constructive progress."

"Poetry is the synthesis of hyacinths and biscuits."

"Chemical synthesis is one of the key technologies that form the basis of modern drug discovery and development. For the rapid preparation of new test compounds and the development of candidates with often highly complex chemical structures, it is essential to use state-of-theart chemical synthesis technologies."